Azeotrope-like compositions of pentafluoropropane and chloropropane

ABSTRACT

This invention provides azeotrope-like compositions of 1,1,1,3,3-pentafluoropropane and 2-chloropropane that are environmentally desirable for use as refrigerants, aerosol propellants, metered dose inhalers, blowing agents for polymer foam, heat transfer media, and gaseous dielectrics.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 10/885,434 (pending), filed Jul. 6, 2004, which is a divisionalof U.S. patent application Ser. No. 10/454,310 (now patented as U.S.Pat. No. 6,787,513), filed Jun. 4, 2003.

FIELD OF THE INVENTION

The present invention relates to azeotrope-like compositions ofpentaflluoropropane and chloropropane, to methods of using suchcompositions, and to blown foams formed using such compositions.

BACKGROUND

Fluorocarbon based fluids have found widespread use in industry in anumber of applications, including, as refrigerants, aerosol propellants,blowing agents, heat transfer media, and gaseous dielectrics. Because ofthe suspected environmental problems associated with the use of some ofthese fluids, especially chlorofluorocarbons (“CFCs”), it is desirableto use fluids of lesser ozone depletion potential such ashydrofluorocarbons, (“HFCs”) and/or hydrochlorofluorocarbons (“HCFCs).

Thus, the use of fluids that do not contain CFCs or contain HCFCs orHFCs instead of CFCs is desirable. Additionally, it is known that theuse of single component fluids or azeotropic mixtures, which mixtures donot fractionate on boiling and evaporation, is preferred in manyapplication, including as blowing agents in for the production of foams.For example, low-density rigid foams, such as polyurethane andpolyisocyanurate foams, are used in a wide variety of applicationsincluding insulation for roofing systems, building panels, refrigeratorsand freezers. To be useful in such applications, it is critical for thefoams to exhibit, among other properties, relatively high thermalinsulation. One measure of a foam s thermal insulation properties is itsk-factor. The term k-factor refers generally to the rate of transfer ofheat energy by conduction through one square foot of one inch thickhomogenous material in one hour where there is a difference of onedegree Fahrenheit perpendicularly across the two surfaces of thematerial. Since the utility of many closed-cell foams is based, at leastin part, upon their thermal insulation properties, it is advantageousand desirable to produce rigid foams having low k-factors.

Known methods for producing rigid foams generally comprise reacting anorganic polyisocyanurate and a polyol in the presence of a blowing agentto form a rigid foam. See, for example, Saunders and Frisch, Volumes Iand II Polyurethanes Chemistry and Technology (1962), which isincorporated herein by reference. While the thermal properties of foamsproduced by these conventional methods may be adequate for selectedapplications, there is a constant need in the art to identify methodsfor producing foams having k-factors at least as low or lower than thoseproduced via conventional methods.

However, the identification of new, environmentally safe, azeotropicmixtures, particularly those well suited for use as blowing agents, iscomplicated due to the fact that azeotrope formation is not readilypredictable.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present inventors have developed compositions that can help tosatisfy the continuing need for substitutes for CFCs and HCFCs. In oneembodiment, the present invention provides azeotrope-like compositionscomprising 1,1,1,3,3-pentafluoropropane (HFC-245fa) and 2-chloropropane.

The preferred compositions of the invention provide environmentallydesirable replacements for currently used CFC s and HCFC s.Additionally, the compositions of the invention exhibit characteristicsthat make the compositions better CFC and HCFC substitutes than eitherof 1,1,1,3,3-pentafluoropropane or 2-chloropropane alone.

One aspect of the invention provides a method for producing foams,preferably foams with relatively low k-factors. Applicants havediscovered that foam blowing agents which comprise the compositions ofthe present invention are unexpectedly capable of providing foams andmethods for producing foams with substantial advantage over prior foamsand processes. More particularly, applicants have counter-intuitivelydiscovered that the use of compositions comprising chloropropane andHFC-245fa as a blowing agent produces foam cells that have a higherpercentage of HFC-245 in the cell gas than when HFC-245fa is used aloneas the blowing agent. This aspect of the present intention can be anadvantage in certain embodiments, especially those requiring a foam withimproved flammability resistance and/or thermal properties. This isbecause HFC′ 245fa is less flammable than and/or has thermal propertiessuperior to many of the other ingredients in the foamable composition,including alternative blowing the agents. In preferred embodiments, thepresent invention provides blowing agent comprising, and preferablyconsisting of, from about 20 wt % to about 80 wt % HFC-245fa and fromabout 20 wt % to about 80 wt % of 2-chloropropoane, and even morepreferably from about 25 wt % to about 75 wt % HFC-245fa and from about25 wt % to 75 wt % of 2-chloropropoane.

The blowing agent aspects of the present invention do not necessarilyrequire that the HFC-245fa/2-chloropropane is present in the form of anazeotrope-like composition. It is contemplated, however, that thepreferred blowing agents of the present invention will compriseazeotrope-like compositions of pentaflluoropropane and chloropropane.

The preferred foams of the present invention preferably have closedcells containing gas comprising HFC-245fa in a concentration that is atleast about 1.5 times, and even more preferably at least about 2 times,the concentration of HFC-245fa in the foamable composition used to formthe foam. In certain preferred embodiments, the foams of the presentinvention have closed cells containing gas comprising HFC-245fa in aconcentration that is greater than 3 times the concentration ofHFC-245fa in the blowing agent used.

Preferred forms to the present invention also exhibit the ability ofinhibiting undesirable decomposition during the foaming reaction.

Another aspect of the present invention is a closed-cell foam producedaccording to the methods of the present invention.

Another aspect of the present invention is the provision ofazeotrope-like compositions. As used herein, the term azeotrope-like isintended in its broad sense to include both compositions that arestrictly azeotropic and compositions that behave like azeotropicmixtures. From fundamental principles, the thermodynamic state of afluid is defined by pressure, temperature, liquid composition, and vaporcomposition. An azeotropic mixture is a system of two or more componentsin which the liquid composition and vapor composition are equal at thestate pressure and temperature. In practice, this means that thecomponents of an azeotropic mixture are constant boiling and cannot beseparated during a phase change.

As the term is used herein, azeotrope-like compositions behave likeazeotropic mixtures, that is, they are constant boiling or essentiallyconstant boiling. In other words, for azeotrope-like compositions, thecomposition of the vapor formed during boiling or evaporation isidentical, or substantially identical, to the original liquidcomposition. Thus, with boiling or evaporation, the liquid compositionchanges, if at all, only to a minimal or negligible extent. This is tobe contrasted with non-azeotrope-like compositions in which, duringboiling or evaporation, the liquid composition changes to a substantialdegree. All azeotrope-like compositions of the invention within theindicated ranges as well as certain compositions outside these rangesare azeotrope-like.

The azeotrope-like compositions of the invention may include additionalcomponents that do not form new azeotropic or azeotrope-like systems, oradditional components that are not in the first distillation cut. Thefirst distillation cut is the first cut taken after the distillationcolumn displays steady state operation under total reflux conditions.One way to determine whether the addition of a component forms a newazeotropic or azeotrope-like system so as to be outside of thisinvention is to distill a sample of the composition with the componentunder conditions that would be expected to separate a non-azeotropicmixture into its separate components. If the mixture containing theadditional component is non-azeotropic or non-azeotrope-like, theadditional component will fractionate from the azeotropic orazeotrope-like components. If the mixture is azeotrope-like, some finiteamount of a first distillation cut will be obtained that contains all ofthe mixture components that is constant boiling or behaves as a singlesubstance.

It follows from this that another characteristic of azeotrope-likecompositions is that there is a range of compositions containing thesame components in varying proportions that are azeotrope-like orconstant boiling. All such compositions are intended to be covered bythe terms azeotrope-like and constant boiling. As an example, it is wellknown that at differing pressures, the composition of a given azeotropewill vary at least slightly, as does the boiling point of thecomposition. Thus, an azeotrope of A and B represents a unique type ofrelationship, but with a variable composition depending on temperatureand/or pressure. It follows that, for azeotrope-like compositions, thereis a range of compositions containing the same components in varyingproportions that are azeotrope-like. All such compositions are intendedto be covered by the term azeotrope-like as used herein.

The present invention provides azeotrope and azeotrope-like compositionscomprising 1,1,1,3,3-pentafluoropropane and 2-chloropropane. Preferably,the novel azeotrope-like compositions of the present invention compriseeffective amounts of 1,1,1,3,3-pentafluoropropane and 2-chloropropane.The term effective amounts as used herein refers to the amount of eachcomponent which upon combination with the other component or components,results in the formation of the present azeotrope-like compositions.

These embodiments preferably provide azeotrope-like compositionscomprising, and preferably consisting essentially of, from about 10 toabout 99 parts by weight HFC-245fa, and from about 1 to about 90 partsby weight of 2-chloropropane, more preferably from about 40 to about 99parts by weight HFC-245fa, and from about 1 to about 60 parts by weightof 2-chloropropane, and even more preferably from about 60 to about 98parts by weight HFC-245fa, and from about 2 to about 40 parts by weightof 2-chloropropane. In highly preferred embodiments, the presentcompositions consist essentially of from about 90 to about 99 parts byweight HFC-245fa and from about 1 to about 10 parts by weight of2-chloropropane, and even more preferably from about 95 to about 99parts by weight HFC-245fa and from about 1 to about 5 parts by weight of2-chloropropane.

Preferred compositions of the present invention are characterized by aboiling point of about 14.54° C.±4° C., preferably ±2° C., morepreferably ±1° C. at 14.49 psia.

Table 1 below provides boiling point data for compositions according topreferred embodiments of the present invention.

TABLE 1 Wt % 2-chloropropane Boiling Pt. (with the remainder being245fa) (° C. at 14.49 psia) 0 14.61 0.19 14.56 0.57 14.56 1.31 14.552.05 14.54 2.77 14.55 4.18 14.56 5.55 14.57 6.89 14.63 8.19 14.67 9.4514.74 10.67 14.80 11.87 14.85 13.03 14.91 14.16 14.97 15.27 15.04 16.3415.12 17.39 15.15 18.41 15.23 19.41 15.29 20.39 15.35

The compositions of the present invention may be used in a wide varietyof applications as substitutes for CFCs and for compositions containingless desirable HCFCs. For example, the present compositions are usefulas solvents, blowing agents, refrigerants, cleaning agents and aerosols.

One embodiment of the present invention relates to a blowing agentcomprising one or more of the present compositions. In otherembodiments, the invention provides foamable compositions, andpreferably polyurethane and polyisocyanurate foam compositions, andmethods of preparing foams. In such foam embodiments, one or more of thepresent compositions, and preferably azeotrope-like compositions, areincluded as a blowing agent in a foamable composition, which compositionpreferably includes one or more additional components capable ofreacting and foaming under the proper conditions to form a foam orcellular structure, as is well known in the art. The present methodspreferably comprise providing such a foamable composition and reactingit under conditions effective to obtain a foam, and preferably a closedcell foam. The invention also relates to foam, and preferably closedcell foam, prepared from a polymer foam formulation containing a blowingagent comprising a composition of the present invention, and preferablyan azeotrope-like composition of the invention.

Any of the methods well known in the art, such as those described inPolyurethanes Chemistry and Technology, Volumes I and II, Saunders andFrisch, 1962, John Wiley and Sons, New York, N.Y., which is incorporatedherein by reference, may be used or adapted for use in accordance withthe foam embodiments of the present invention. In general, suchpreferred methods comprise preparing polyurethane or polyisocyanuratefoams by combining I hit arean isocyanate, a polyol or mixture ofpolyols, a blowing agent or mixture of blowing agents comprising one ormore of the present compositions, and other materials such as catalystso well as, surfactants, and optionally, flame retardants, colorants, orother additives. It is convenient in many applications to provide thecomponents for polyurethane or polyisocyanurate foams in pre-blendedformulations. Most typically, the foam formulation is pre-blended intotwo components. The isocyanate and optionally certain surfactants andblowing agents comprise the first component, commonly referred to as theA component. The polyol or polyol mixture, surfactant, catalysts,blowing agents, flame retardant, and other isocyanate reactivecomponents comprise the second component, commonly referred to as the Bcomponent. Accordingly, polyurethane or polyisocyanurate foams arereadily prepared by bringing together the A and B side components eitherby hand mix for small preparations and, preferably, machine mixtechniques to form blocks, slabs, laminates, pour-in-place panels andother items, spray applied foams, froths, and the like. Optionally,other ingredients such as fire retardants, colorants, auxiliary blowingagents, and even other polyols can be added as a third stream to the mixhead or reaction site. Most conveniently, however, they are allincorporated into one B-component as described above.

It is also possible to produce thermoplastic foams using thecompositions of the invention. For example, conventional foampolyurethanes and isocyanurate formulations may be combined with theazeotrope-like compositions in a conventional manner to produce rigidfoams.

Azeotrope-like mixtures containing HFC-245fa in accordance with thepresent invention are particularly suitable as foam blowing agents sincefoams blown with HFC-245fa have been found to possess low relativeinitial and aged thermal conductivity and good dimensional stability atlow temperatures. Of particular interest are those azeotrope-likecompositions of the present invention that optionally further containother zero or low ozone depleting materials, such as, for example, otherhydrofluorocarbons, e.g., difluoromethane (HFC-32); difluoroethane(HFC-152); trifluoroethane (HFC-143); tetrafluoroethane (HFC-134);pentafluoroethane (HFC-125); pentafluoropropane (HFC-245);hexafluoropropane (HFC-236); heptafluoropropane (HFC-227);pentafluorobutane (HFC-365) and inert gases, e.g., air, nitrogen, carbondioxide. Where isomerism is possible for the hydrofluorocarbonsmentioned above, the respective isomers may be used either singly or inthe form of a mixture.

Dispersing agents, cell stabilizers, and surfactants may also beincorporated into the blowing agent mixture. Surfactants, most notablysilicone oils, are added to serve as cell stabilizers. Somerepresentative materials are sold under the names of DC-193, B-8404, andL-5340 which are, generally, polysiloxane polyoxyalkylene blockco-polymers such as those disclosed in U.S. Pat. Nos. 2,834,748,2,917,480, and 2,846,458. Other optional additives for the blowing agentmixture may include flame retardants such astri(2-chloroethyl)phosphate, tri(2-chloropropyl)phosphate,tri(2,3-dibromopropyl)-phosphate, tri(1,3-dichloropropyl)phosphate,diammonium phosphate, various halogenated aromatic compounds, antimonyoxide, aluminum trihydrate, polyvinyl chloride, and the like.

In another embodiment, the azeotrope-like compositions of this inventionmay be used as propellants in sprayable compositions, either alone or incombination with known propellants.

The sprayable composition comprises, consists essentially of, andconsists of a material to be sprayed and a propellant comprising,consisting essentially of, and consisting of the azeotrope-likecompositions of the invention. Inert ingredients, solvents, and othermaterials may also be present in the sprayable mixture. Preferably, thesprayable composition is an aerosol. Suitable materials to be sprayedinclude, without limitation, cosmetic materials such as deodorants,perfumes, hair sprays, cleansers, and polishing agents as well asmedicinal materials such as anti-asthma and anti-halitosis medications.

In general, the amount of blowing agent present in the blended mixtureused to form the foamable composition of the present invention isdictated by the desired foam densities of the final polyurethane orpolyisocyanurate foams products. The polyurethane foams produced canvary in density from about 0.5 pound per cubic foot to about 40 poundsper cubic foot, preferably from about 1.0 to about 20.0 pounds per cubicfoot, and most preferably from about 1.5 to about 6.0 pounds per cubicfoot for rigid polyurethane foams and from about 1.0 to about 4.0 poundsper cubic foot for flexible foams. The density obtained is a function ofseveral factors, including how much of the blowing agent, or blowingagent mixture, is present in the A and/or B components, or that is addedat the time the foam is prepared.

The components of the composition of the invention are known materialsthat are commercially available or may be prepared by known methods.Preferably, the components are of sufficiently high purity so as toavoid the introduction of adverse influences upon cooling or heatingproperties, constant boiling properties, or blowing agent properties ofthe system. In the case of metered dose inhalers, the relevant currentGood Manufacturing Process may be used for manufacturing thesematerials.

Additional components may be added to tailor the properties of theazeotrope-like compositions of the invention as needed. By way ofexample, oil solubility aids may be added in the case in which thecompositions of the invention are used as refrigerants. Stabilizers andother materials may also be added to enhance the properties of thecompositions of the invention.

EXAMPLES Example 1

An ebulliometer consisting of vacuum jacketed tube with a condenser ontop was used. About 25 g HFC-245fa is charged to the ebulliometer andthen 2-chloropropane is added in small, measured increments. Temperaturedepression is observed when the 2-chloropropoane is added to theHFC-245fa, indicating a minimum boiling azeotrope is formed. From justabove zero weight percent to about 3.5 weight percent of2-chloropropane, the boiling point of the composition changes by about0.05 C. Therefore, the composition exhibits azeotrope and/orazeotrope-like properties over this range.

Example 2

One aspect of the invention is further illustrated by the followingexample, in which parts or percentages are by weight unless otherwisespecified. The following materials are used in the example.

Polyol: A polyester polyol with an OH number of 240 containing acompatibilizer to aid miscibility.

HFC-245fa

2-chloropropane

Surfactant A: A polysiloxane polyether surfactant

Catalyst B: A trimerization catalyst

Three foams (AExperiment 1,″Experiment 2 and AExperiment 3″) areprepared by a general procedure commonly referred to as Ahandmixing@.For each blowing agent, a premix of polyol, surfactant, and catalysts isprepared in the proportions indicated in Table 2. About 100 grams ofeach formulation is blended. The premix is blended in a 32 oz paint can,and stirred at about 1500 rpm with a Conn 2@ diameter ITC mixer until ahomogeneous blend is achieved.

When mixing is complete, the can containing the mix is covered andplaced in a refrigerator controlled at 50° F. The foam blowing agent orpre-blended pair of blowing agents for experiment 1 is also stored inpressure bottles at 50° F. The A-component is kept in sealed containersat 70° F.

The pre-cooled blowing agent is added in the indicated amount to thepremix. The contents are stirred for two minutes with a Conn 2 @ ITCmixing blade turning at 1000 rpm. Following this, the mixing vessel andcontents are reweighed. If there is a weight loss, the blowing agent iadded to the solution to make up any weight loss. The can is thancovered and replaced in the refrigerator.

After the contents had cooled again to 50° F., approximately 10 minutes,the mixing vessel is removed from refrigerator and taken to the mixingstation. A pre-weighted portion of A-component, isocyanurate, is addedquickly to the B-component, the ingredients mixed for 10 seconds using aConn 2@ diameter ITC mixing blade at 3000 rpm and poured into a 8@×8@×4@cardboard cake box and allowed to rise. The resulting rigid foam isinspected and found to be of good quality. The composition of the gascontained in the cells of the foam is analyzed and found to have theconcentrations indicated in Table 2.

TABLE 2 Component Experiment 1 Experiment 2 Experiment 3 Blowing Agent,Wt % 2-Chloropropane 0 25 75 245fa 100 75 25 Foam Formulation, gmPolyester polyol 100 100 100 Silicone surfactant 2 2 2 Phosphorous flameret 5 5 5 Catalyst A 0.3 0.3 0.3 Catalyst B 3.6 3.6 3.6 Water 0.5 0.50.5 2-chloropropane 0 6.4 20.25 245fa 51.5 36.6 12.88 Cell Gas, Wt %2-chloropropane 0 8.21 42.14 245fa 58.62 69.27 32.47 Nitrogen 29.81 17.719.37 Oxygen 10.14 3.9 4.19 Carbon Dioxide 0.22 0.27 0.53 Other 1.210.65 1.30

As can be seen from the results of Example 2, the use of a compositionof the present invention as a blowing agent results in a relatively highlevel of retention of HCFC-245fa in the foam cell. More particularly,the concentration of HCFC-245fa in the cell gas in Experiment 2 isgreater than about 1.5 times the concentration in the foamablecomposition.

1. A method for producing polyurethane and polyisocyanurate foamscomprising reacting and foaming a mixture of ingredients that react toform the polyurethane and polyisocyanurate foams in the presence of avolatile blowing agent comprising azeotrope-like compositions consistingessentially of from about 1 to about 90 weight percent 2-chloropropaneand from about 10 to about 99 weight percent HFC-245fa.
 2. The method ofclaim 1 wherein said azeotrope-like compositions consist essentially offrom about 1 to about 40 weight percent 2-chloropropane and from about60 to about 99 weight percent HFC-245fa.
 3. The method of claim 2wherein said azeotrope-like compositions consist essentially of fromabout 1 to about 10 weight percent 2-chloropropane and from about 99 toabout 90 weight percent HFC-245fa.
 4. A closed cell foam containing acell gas comprising an azeotrope-like composition consisting essentiallyof from about 1 to about 90 weight percent 2-chloropropane and fromabout 10 to about 99 weight percent HFC-245fa.
 5. The closed cell foamof claim 4 wherein said azeotrope-like compositions consist essentiallyof from about 1 to about 40 weight percent 2-chloropropane and fromabout 60 to about 99 weight percent HFC-245fa.
 6. The closed cell foamof claim 5 wherein said azeotrope-like compositions consist essentiallyof from about 1 to about 10 weight percent 2-chloropropane and fromabout 99 to about 90 weight percent HFC-245fa.
 7. A sprayablecomposition comprising a material to be sprayed and a propellantconsisting essentially of from about 1 to about 90 weight percent2-chloropropane and from about 10 to about 99 weight percent HFC-245fa.8. The sprayable composition according to claim 7 wherein the sprayablecomposition is an aerosol.
 9. The sprayable composition according toclaim 8 wherein the sprayable composition is a cosmetic material. 10.The sprayable composition of claim 8 wherein the material to be sprayedis a medicinal material.